<?php
/*
 *  $Id$
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.doctrine-project.org>.
 */

namespace Doctrine\ORM\Query;

/**
 * Represents a chain of tree walkers that modify an AST and finally emit output.
 * Only the last walker in the chain can emit output. Any previous walkers can modify
 * the AST to influence the final output produced by the last walker.
 * 
 * @author Roman Borschel <roman@code-factory.org>
 * @since 2.0
 */
class TreeWalkerChain implements TreeWalker {
	/** The tree walkers. */
	private $_walkers = array();
	/** The original Query. */
	private $_query;
	/** The ParserResult of the original query that was produced by the Parser. */
	private $_parserResult;
	/** The query components of the original query (the "symbol table") that was produced by the Parser. */
	private $_queryComponents;
	
	/**
	 * @inheritdoc
	 */
	public function __construct($query, $parserResult, array $queryComponents) {
		$this->_query = $query;
		$this->_parserResult = $parserResult;
		$this->_queryComponents = $queryComponents;
	}
	
	/**
	 * Adds a tree walker to the chain.
	 * 
	 * @param string $walkerClass The class of the walker to instantiate.
	 */
	public function addTreeWalker($walkerClass) {
		$this->_walkers[] = new $walkerClass( $this->_query, $this->_parserResult, $this->_queryComponents );
	}
	
	/**
	 * Walks down a SelectStatement AST node, thereby generating the appropriate SQL.
	 *
	 * @return string The SQL.
	 */
	public function walkSelectStatement(AST\SelectStatement $AST) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSelectStatement( $AST );
		}
	}
	
	/**
	 * Walks down a SelectClause AST node, thereby generating the appropriate SQL.
	 *
	 * @return string The SQL.
	 */
	public function walkSelectClause($selectClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSelectClause( $selectClause );
		}
	}
	
	/**
	 * Walks down a FromClause AST node, thereby generating the appropriate SQL.
	 *
	 * @return string The SQL.
	 */
	public function walkFromClause($fromClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkFromClause( $fromClause );
		}
	}
	
	/**
	 * Walks down a FunctionNode AST node, thereby generating the appropriate SQL.
	 *
	 * @return string The SQL.
	 */
	public function walkFunction($function) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkFunction( $function );
		}
	}
	
	/**
	 * Walks down an OrderByClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param OrderByClause
	 * @return string The SQL.
	 */
	public function walkOrderByClause($orderByClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkOrderByClause( $orderByClause );
		}
	}
	
	/**
	 * Walks down an OrderByItem AST node, thereby generating the appropriate SQL.
	 *
	 * @param OrderByItem
	 * @return string The SQL.
	 */
	public function walkOrderByItem($orderByItem) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkOrderByItem( $orderByItem );
		}
	}
	
	/**
	 * Walks down a HavingClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param HavingClause
	 * @return string The SQL.
	 */
	public function walkHavingClause($havingClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkHavingClause( $havingClause );
		}
	}
	
	/**
	 * Walks down a JoinVariableDeclaration AST node and creates the corresponding SQL.
	 *
	 * @param JoinVariableDeclaration $joinVarDecl
	 * @return string The SQL.
	 */
	public function walkJoinVariableDeclaration($joinVarDecl) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkJoinVariableDeclaration( $joinVarDecl );
		}
	}
	
	/**
	 * Walks down a SelectExpression AST node and generates the corresponding SQL.
	 *
	 * @param SelectExpression $selectExpression
	 * @return string The SQL.
	 */
	public function walkSelectExpression($selectExpression) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSelectExpression( $selectExpression );
		}
	}
	
	/**
	 * Walks down a QuantifiedExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param QuantifiedExpression
	 * @return string The SQL.
	 */
	public function walkQuantifiedExpression($qExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkQuantifiedExpression( $qExpr );
		}
	}
	
	/**
	 * Walks down a Subselect AST node, thereby generating the appropriate SQL.
	 *
	 * @param Subselect
	 * @return string The SQL.
	 */
	public function walkSubselect($subselect) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSubselect( $subselect );
		}
	}
	
	/**
	 * Walks down a SubselectFromClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param SubselectFromClause
	 * @return string The SQL.
	 */
	public function walkSubselectFromClause($subselectFromClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSubselectFromClause( $subselectFromClause );
		}
	}
	
	/**
	 * Walks down a SimpleSelectClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param SimpleSelectClause
	 * @return string The SQL.
	 */
	public function walkSimpleSelectClause($simpleSelectClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSimpleSelectClause( $simpleSelectClause );
		}
	}
	
	/**
	 * Walks down a SimpleSelectExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param SimpleSelectExpression
	 * @return string The SQL.
	 */
	public function walkSimpleSelectExpression($simpleSelectExpression) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSimpleSelectExpression( $simpleSelectExpression );
		}
	}
	
	/**
	 * Walks down an AggregateExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param AggregateExpression
	 * @return string The SQL.
	 */
	public function walkAggregateExpression($aggExpression) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkAggregateExpression( $aggExpression );
		}
	}
	
	/**
	 * Walks down a GroupByClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param GroupByClause
	 * @return string The SQL.
	 */
	public function walkGroupByClause($groupByClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkGroupByClause( $groupByClause );
		}
	}
	
	/**
	 * Walks down a GroupByItem AST node, thereby generating the appropriate SQL.
	 *
	 * @param GroupByItem
	 * @return string The SQL.
	 */
	public function walkGroupByItem(AST\PathExpression $pathExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkGroupByItem( $pathExpr );
		}
	}
	
	/**
	 * Walks down an UpdateStatement AST node, thereby generating the appropriate SQL.
	 *
	 * @param UpdateStatement
	 * @return string The SQL.
	 */
	public function walkUpdateStatement(AST\UpdateStatement $AST) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkUpdateStatement( $AST );
		}
	}
	
	/**
	 * Walks down a DeleteStatement AST node, thereby generating the appropriate SQL.
	 *
	 * @param DeleteStatement
	 * @return string The SQL.
	 */
	public function walkDeleteStatement(AST\DeleteStatement $AST) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkDeleteStatement( $AST );
		}
	}
	
	/**
	 * Walks down a DeleteClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param DeleteClause
	 * @return string The SQL.
	 */
	public function walkDeleteClause(AST\DeleteClause $deleteClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkDeleteClause( $deleteClause );
		}
	}
	
	/**
	 * Walks down an UpdateClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param UpdateClause
	 * @return string The SQL.
	 */
	public function walkUpdateClause($updateClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkUpdateClause( $updateClause );
		}
	}
	
	/**
	 * Walks down an UpdateItem AST node, thereby generating the appropriate SQL.
	 *
	 * @param UpdateItem
	 * @return string The SQL.
	 */
	public function walkUpdateItem($updateItem) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkUpdateItem( $updateItem );
		}
	}
	
	/**
	 * Walks down a WhereClause AST node, thereby generating the appropriate SQL.
	 *
	 * @param WhereClause
	 * @return string The SQL.
	 */
	public function walkWhereClause($whereClause) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkWhereClause( $whereClause );
		}
	}
	
	/**
	 * Walks down a ConditionalExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param ConditionalExpression
	 * @return string The SQL.
	 */
	public function walkConditionalExpression($condExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkConditionalExpression( $condExpr );
		}
	}
	
	/**
	 * Walks down a ConditionalTerm AST node, thereby generating the appropriate SQL.
	 *
	 * @param ConditionalTerm
	 * @return string The SQL.
	 */
	public function walkConditionalTerm($condTerm) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkConditionalTerm( $condTerm );
		}
	}
	
	/**
	 * Walks down a ConditionalFactor AST node, thereby generating the appropriate SQL.
	 *
	 * @param ConditionalFactor
	 * @return string The SQL.
	 */
	public function walkConditionalFactor($factor) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkConditionalFactor( $factor );
		}
	}
	
	/**
	 * Walks down a ConditionalPrimary AST node, thereby generating the appropriate SQL.
	 *
	 * @param ConditionalPrimary
	 * @return string The SQL.
	 */
	public function walkConditionalPrimary($condPrimary) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkConditionalPrimary( $condPrimary );
		}
	}
	
	/**
	 * Walks down an ExistsExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param ExistsExpression
	 * @return string The SQL.
	 */
	public function walkExistsExpression($existsExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkExistsExpression( $existsExpr );
		}
	}
	
	/**
	 * Walks down a CollectionMemberExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param CollectionMemberExpression
	 * @return string The SQL.
	 */
	public function walkCollectionMemberExpression($collMemberExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkCollectionMemberExpression( $collMemberExpr );
		}
	}
	
	/**
	 * Walks down an EmptyCollectionComparisonExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param EmptyCollectionComparisonExpression
	 * @return string The SQL.
	 */
	public function walkEmptyCollectionComparisonExpression($emptyCollCompExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkEmptyCollectionComparisonExpression( $emptyCollCompExpr );
		}
	}
	
	/**
	 * Walks down a NullComparisonExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param NullComparisonExpression
	 * @return string The SQL.
	 */
	public function walkNullComparisonExpression($nullCompExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkNullComparisonExpression( $nullCompExpr );
		}
	}
	
	/**
	 * Walks down an InExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param InExpression
	 * @return string The SQL.
	 */
	public function walkInExpression($inExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkInExpression( $inExpr );
		}
	}
	
	/**
	 * Walks down an InstanceOfExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param InstanceOfExpression
	 * @return string The SQL.
	 */
	function walkInstanceOfExpression($instanceOfExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkInstanceOfExpression( $instanceOfExpr );
		}
	}
	
	/**
	 * Walks down a literal that represents an AST node, thereby generating the appropriate SQL.
	 *
	 * @param mixed
	 * @return string The SQL.
	 */
	public function walkLiteral($literal) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkLiteral( $literal );
		}
	}
	
	/**
	 * Walks down a BetweenExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param BetweenExpression
	 * @return string The SQL.
	 */
	public function walkBetweenExpression($betweenExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkBetweenExpression( $betweenExpr );
		}
	}
	
	/**
	 * Walks down a LikeExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param LikeExpression
	 * @return string The SQL.
	 */
	public function walkLikeExpression($likeExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkLikeExpression( $likeExpr );
		}
	}
	
	/**
	 * Walks down a StateFieldPathExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param StateFieldPathExpression
	 * @return string The SQL.
	 */
	public function walkStateFieldPathExpression($stateFieldPathExpression) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkStateFieldPathExpression( $stateFieldPathExpression );
		}
	}
	
	/**
	 * Walks down a ComparisonExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param ComparisonExpression
	 * @return string The SQL.
	 */
	public function walkComparisonExpression($compExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkComparisonExpression( $compExpr );
		}
	}
	
	/**
	 * Walks down an InputParameter AST node, thereby generating the appropriate SQL.
	 *
	 * @param InputParameter
	 * @return string The SQL.
	 */
	public function walkInputParameter($inputParam) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkInputParameter( $inputParam );
		}
	}
	
	/**
	 * Walks down an ArithmeticExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param ArithmeticExpression
	 * @return string The SQL.
	 */
	public function walkArithmeticExpression($arithmeticExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkArithmeticExpression( $arithmeticExpr );
		}
	}
	
	/**
	 * Walks down an ArithmeticTerm AST node, thereby generating the appropriate SQL.
	 *
	 * @param mixed
	 * @return string The SQL.
	 */
	public function walkArithmeticTerm($term) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkArithmeticTerm( $term );
		}
	}
	
	/**
	 * Walks down a StringPrimary that represents an AST node, thereby generating the appropriate SQL.
	 *
	 * @param mixed
	 * @return string The SQL.
	 */
	public function walkStringPrimary($stringPrimary) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkStringPrimary( $stringPrimary );
		}
	}
	
	/**
	 * Walks down an ArithmeticFactor that represents an AST node, thereby generating the appropriate SQL.
	 *
	 * @param mixed
	 * @return string The SQL.
	 */
	public function walkArithmeticFactor($factor) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkArithmeticFactor( $factor );
		}
	}
	
	/**
	 * Walks down an SimpleArithmeticExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param SimpleArithmeticExpression
	 * @return string The SQL.
	 */
	public function walkSimpleArithmeticExpression($simpleArithmeticExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkSimpleArithmeticExpression( $simpleArithmeticExpr );
		}
	}
	
	/**
	 * Walks down an PathExpression AST node, thereby generating the appropriate SQL.
	 *
	 * @param mixed
	 * @return string The SQL.
	 */
	public function walkPathExpression($pathExpr) {
		foreach( $this->_walkers as $walker ) {
			$walker->walkPathExpression( $pathExpr );
		}
	}
	
	/**
	 * Gets an executor that can be used to execute the result of this walker.
	 * 
	 * @return AbstractExecutor
	 */
	public function getExecutor($AST) {}
}